The present invention relates to a pressure sensor apparatus having a pressure sensor element for measuring the pressure of a gas, and a pressure sensor housing for containing the pressure sensor element.
An example of a pressure sensor apparatus that is set up in an intake manifold of a vehicle and measures the pressure of air in the manifold is shown in FIG. 7 through FIG. 9. FIG. 7 is a plan view of a pressure sensor apparatus 100, FIG. 8 is a cross-sectional view taken along a line B-B of FIG. 7, and FIG. 9 is a perspective view of a pressure sensor housing 100′ formed by removing a pressure sensor element 201 and a sensor mount portion 202 from the pressure sensor apparatus 100 shown in FIG. 8.
As shown in FIG. 8, a pressure detection chamber 102 is formed in a substantially central part of a sensor housing main body 101, and a pressure inlet 103 communicating with a lower portion of the pressure detection chamber 102. Reference numeral 104 represents a pressure introducing pipe that has the pressure inlet 103 at the center. The pressure introducing pipe 104 is inserted into the intake manifold (not shown) such that a seating surface 109 of the sensor housing main body 101 contacts with the intake manifold. The pressure introducing pipe 104 introduces the air inside the intake manifold from the pressure inlet 103 to the pressure detection chamber 102. A gasket 111 is provided on the pressure introducing pipe 104 to prevent air from leaking out of the manifold during engine operation. Reference numeral 107 shown in FIG. 7 through FIG. 9 is a mounting hole for fixing the pressure sensor apparatus 100 to the intake manifold by a screw, bolt or some other mechanical fastener.
Furthermore, reference numeral 201 represents a pressure sensor element composed of a semiconductor, and this pressure sensor element 201 is mounted in the sensor mount portion 202 and disposed above the pressure detection chamber 102. The pressure sensor element 201 is formed by bridge-connecting a plurality of semiconductor strain gauges formed on a diaphragm composed of single-crystal silicon or the like. When the diaphragm is deformed by a change of pressure in the pressure detection chamber 102, the resistance of the semiconductor strain gauges is changed by a piezoelectric effect in accordance with the volume of the deformation. By this principle, the pressure of the pressure detection chamber 102, which is the air pressure within the intake manifold, can be detected by detecting a voltage signal equivalent to the gauge resistance ratio.
Moreover, reference numeral 203 shown in FIG. 8 represents a lead terminal, and this lead terminal 203 is connected to the pressure sensor element 201 via a bonding wire (not shown). Also, reference numeral 204 represents another lead terminal, and this lead terminal 204 is connected to the lead terminal 203 by welding or the like. The lead terminal 204 projects toward the inside of a connector socket 105, and a connector (not shown) for extracting an output signal of the pressure sensor element 201 is attached to the connector socket 105. Reference numeral 102b represents the bottom surface of the pressure detection chamber 102. The pressure sensor element 201 and the bonding wire (not shown) are protected by a gel-like coating member, which is not shown, to protect a wiring section from being corroded by moisture, depleted oil, gasoline or the like entering from the outside.
As shown in FIG. 8 and FIG. 9, a substantially semicircular and flat protective wall 106 is provided horizontally in a protruding fashion on an inner peripheral wall of the sensor housing main body 101 that faces the pressure detection chamber 102. A top surface 113 of the protective wall 106 is in a plane that is parallel with a plane of the seating surface of the sensor housing main body 101 such that the two planes do not intersect. The protective wall 106 prevents oil, dust and other foreign matters from entering the pressure detection chamber 102 from the intake manifold side and prevents damage and contamination of the pressure sensor element 201.
Japanese Unexamined Patent Application Publication No. 2005-345412 A, its corresponding U.S. Pat. No. 7,104,136, Japanese Unexamined Patent Application Publication No. 2002-310836 A and its corresponding U.S. Pat. No. 6,604,430 each describe a conventional technology that has a mechanism for preventing entry of foreign matters into the pressure detection chamber, as with the protective wall 106 described above. In the pressure sensor apparatus according to Japanese Unexamined Patent Application Publication No. 2005-345412 A and its corresponding U.S. Pat. No. 7,104,136, a plurality of compartments are provided on a passage extending from an intake manifold to a pressure sensor element, a flat protruding portion is provided perpendicular to an inner wall of each compartment, and entry of foreign matters into a pressure detection chamber is prevented by these compartments and the projecting portion. In the pressure sensor apparatus and the pressure sensor container according to Japanese Unexamined Patent Application Publication No. 2002-310836 and its corresponding U.S. Pat. No. 6,604,430, a plurality of three-dimensional projecting portions disposed on an inner wall of the pressure introducing pipe prevent entry of foreign matters.
It is assumed that these types of pressure sensor apparatuses are normally attached to an intake manifold horizontally, as shown in FIG. 8. However, there is a case in which the pressure sensor apparatus 100 is disposed at an angle with respect to a horizontal line as shown in FIG. 10, due to the layout and the like of the intake manifold. In such a case, moisture generated by the condensation of air within the pressure detection chamber 102 or moisture that directly enters from the intake manifold is adhered to and accumulated in a space between the flat protective wall 106 and an inner peripheral wall of the pressure detection chamber 102. Reference numeral 301 shown in FIG. 10 represents the abovementioned moisture. When the moisture 301 is frozen in a low-temperature environment, there is a possibility that the diaphragm formed on the surface of the pressure sensor element 201 might be damaged or that the bonding wire might be disconnected. Also, there is a possibility that frozen ice might obstruct the introduction of air into the pressure detection chamber 102.
In addition, not only the abovementioned moisture but also oil or gasoline accumulates on a top surface of the flat protective wall 106, and the gel-like coating member coating the pressure sensor element 201 and the like swells because of the oil or gasoline, whereby a target coating effect cannot be obtained. Therefore, such disadvantages caused by the accumulation of moisture, oil, gasoline or the like in the pressure detection chamber 102 can be generated not only on the protective wall 106 but also the bottom surface 102b of the pressure detection chamber 102. Similar problems can occur in the above-mentioned references in which moisture, oil, gasoline or the like accumulates on the top surfaces of the projecting portions if the pressure sensor apparatus is disposed obliquely. It would be desirable to eliminate this accumulation to ensure proper operation of the sensor.